(1) Field of the Invention
This invention relates generally to retractable hook eyes and more particularly to a retractable pull-down eye for use in hauling a buoyant test vehicle (BTV) down to a release depth below a water surface. The eye is spring loaded to retract into the tail housing of the BTV when released and is shaped to conform to the contour of the tail section of the BTV to minimize turbulence. Channels within the eye or other means are provided to allow water to escape as the eye retracts into its housing. A tapped hole is provided in the eye to extend the eye when attaching the pull-down hook.
(2) Description of the Prior Art
BTV systems are used to test noise generated by shapes moving through a fluid medium. The BTV is configured to conform to the desired shape, hauled down below the water surface and released. Noise measurements are taken as the BTV rises to the surface. Current BTV's use a pull-down eye attached to the tail piece of the BTV together with a well known Benthos acoustic deep sea release. A cable is attached to the eye and the BTV is pulled below the surface. When the desired depth is reached, an acoustic signal is transmitted to the Benthos release which causes the hook on the Benthos release device to open allowing the BTV to ascend. The pull-down eye attached to the ascending BTV generates extraneous noise not corresponding to the shape being tested. To eliminate the extraneous noise, a non-turbulent pull-down eye is required. Further, the pull-down eye must be non-turbulent almost immediately upon release, such that noise measurements will not be adversely impacted.
Lovejoy in U.S. Pat. No. 4,331,096 discloses a retractable pad-eye device having a shape corresponding to the surrounding structure when in its retracted position. However, the device requires a manual operation to change between the pad-eye and the retracted positions. Such a device cannot be used with a self-releasing BTV at substantial depth below the water surface. Spring loaded pad-eyes or cleats are well known in the art. Such devices, as disclosed by Morris in U.S. Pat. No. 4,890,566 and Harris in U.S. Pat. No. 5,004,388, typically provide for the spring action to extend the cleat upon release, rather than retract. No current devices provide the non-turbulent shape combined with the quick retraction required for sensitive noise measurements.